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How do I troubleshoot SIP configurations to solve service issues?

When your SIP service isn't connecting properly, process of elimination will help you determine if the issue lies in your configuration or elsewhere on the network.

Testing methods for Session Initiation Protocol configuration vary from one vendor product to another. Depending on your vendor, testing methods might include troubleshooting tools, recommended courses of action, and in some cases, your carrier may help with discovering the cause of the problem. During your request for information or selection process for a UC vendor, it's beneficial to ask what troubleshooting tools and knowledge transfers are available for setup, testing, troubleshooting SIP and error reporting. It never hurts to enlist your carrier in testing, if possible. The advantage is that vendors have the tools to examine the packets and ports and can provide guidance.

If you don't have the help of your carrier, two methods can be used to troubleshoot SIP configurations on your own:

  • Check that port 5060 or 5061 is open and available in your firewall. Without this, nothing else will work. You may need to enlist the help of your security team to check this out on your corporate network.
  • Test the port is with a telnet client. Once you enable the telnet client, type the following:

telnet [domain name or IP address] [port #]. For example, telnet 5060.

If the port is open you will see a blank screen. If it's not, an error message will indicate the port didn't connect or the server isn't listening on that port.

Make sure the telnet client is calling with or has resolved to an external IP address. Many clients will this by automatically resolving to an email or user ID. It's indicative of a problem if you try to make a call and have silence on the other end. In some cases, you can hang up and reinitiate the call. If the call is successful, the problem may have been a time out from one end to the other. If the call is intermittently in and out, the problem may be the speed or quality of the circuit. If you are operating over Wi-Fi, it may be an issue with access point saturation.

SIP is an open protocol and should be pretty simple to set up and use. If you try one product and it isn't working, you may want to demo another SIP client to see if it works. If you have problems with multiple products on multiple machines, the issue is likely your network's LAN or WAN configuration. Process of elimination is time-consuming, but it can be invaluable when troubleshooting SIP configuration issues.

Do you have a question for Carrie Higbie Goetz or any other experts? Ask your enterprise-specific questions today. (All questions are treated anonymously.)

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